This invention relates to a novel X-ray source.
The invention disclosed is related to copending application, Ser. No. 06/736,136 entitled X-RAY SOURCE TUBE EMPLOYING COLD CATHODE GAS DISCHARGE TUBE WITH COLLIMATED BEAM, filed May 20, 1985, now U.S. Pat. No. 4,670,894, issued June 2, 1987, the disclosure of which is herein incorporated by reference. That application discloses a novel X-ray source which employs a cold cathode, rather than a heated filament cathode. The use of a cold cathode in conjunction with a triode structure results in the emission of X-rays having a constant bremstrahlung spectrum, which is necessary to obtain proper grey scale rendition when the tube is used, for example, for medical diagnostic purposes.
A cold cathode can be configured to provide a relatively wide surface area source of energetic electrons. Such a configuration avoids a high density target region on the anode which is associated with prior art filament heated cathodes. As described in the copending application, a control grid is disposed between the cathode and anode of the X-ray source tube. The control grid ensures the firing and operation of the tube at substantially a constant voltage, thus avoiding a change in KV.sub.peak for the tube and the consequent shift in bremstrahlung content.
The present invention uses a cathode-grid-anode configuration similar to the X-ray source tube described above, but produces the spontaneous emission of X-rays from a working medium in the anode. When the electrons impinge on the anode, X-rays are created and, in particular, flood the hollow center section of the anode which is filled with a working medium. The X-rays, together with the impinging electrons, acts as the pump to produce a population inversion that causes the spontaneous emission of coherent X-rays (which are different from the pumping X-rays produced in the prior invention).
Thus, the present invention provides a novel X-ray source. When the X-ray source of the present invention is arranged in a series of stages, a highly amplified X-ray beam is obtained.